Since the first elections to the Scottish Parliament were held in 1999 the institution's powers have grown considerably.

This will be clear when the finance secretary, the SNP's Derek Mackay, delivers his draft devolved Budget to MSPs on Thursday afternoon.

Following successive further devolution, Holyrood now holds more power over taxation than any of the long established regional bodies in Spain, Germany or Australia.

The Scottish Government's reach extends to your pay packet, as you might be reminded of tomorrow.

Mackay is widely expected to raise income tax in a bid to raise more revenues to support existing public services and a pay rise for those working in them.

"None of us want to see our cherished public services increasingly constrained in what they can deliver," the First Minister said last month.

"So with all the pressures we now face, we must consider if the time has come for those who earn the most to pay a modest amount more to enable us to do so."

How large the tax rise will be and who exactly will be paying more will only become clear when the finance secretary addresses MSPs on Thursday.

Currently, the Scottish income tax regime looks largely similar to that in the rest of the UK.

The only difference is the 40% rate kicks in at £43,000 while in the rest of the country you do not start paying this rate until you earn £45,000.

Mackay can change the thresholds, change the rate of the bands and indeed abolish or create entire new bands.

The only thing the finance secretary cannot touch is the personal allowance, this is the amount of money you are allowed to earn before the taxman starts taking a cut.

This remains reserved to Westminster and is currently £11,500. Come the next financial year in April it will rise to £11,850.

Following the Holyrood election last year, the SNP governs Scotland as a minority administration.

This simply means it does not hold a majority of seats in the chamber can be outvoted if all opposition parties go against them.

As such, the party has to win over the support of at least one of the other parties.

Talks have taken place between the SNP and representative from some of the other parties.

Scottish Labour, the Scottish Liberal Democrats and the Scottish Greens all support varying income tax models but they all have a common theme: some Scots would pay more under their plans.

On the other hand, the Scottish Conservatives are opposed to any change which means Scots are taxed more than their counterparts in England, Wales and Northern Ireland.

Thursday's Budget is technically a draft version. It is what the Scottish Government wants, not necessarily what it will get.

Over the next couple of months the finance committee and MSPs will scrutinise the plans and try to amend aspects which they do not like.

The Budget will then be laid before the parliament as a bill in either in late January or early February, with the Scottish Government hoping it will be passed by the end of February.

The vast majority of Scots are only taxed at the 20% rate.

HMRC estimates around 2.19 million people in Scotland are taxed at the basic rate, while a further 354,000 fall in to to the higher 40% rate.

Only around 20,000 Scottish workers earn enough money to be liable for the 45% top rate of tax.

Despite there not being a lot of them, these people contribute almost 19% of all the income tax collected by the Scottish Government.

The Scottish Government's chief economist issued a pre-Budget warning on Tuesday.

Dr Gary Gillespie published updated advice on what it forecasts would happen if the top rate of tax was increased to 50p in the pound in Scotland while it remained at 45p in the rest of the UK.

The report, which was informed by the First Minister's council of economic advisers, said such a move could actually reduce the amount of money collected by the devolved administration.

This is because it judged the 20,000 or so additional rate payers are "more mobile" than average workers and more likely to minimise their tax liabilities by doing things such as creating companies.

Incorporation allows these professionals to benefit from business taxation rates, which are lower than income tax.

Under the best case scenario, a Scottish 50% rate would net an extra £145m in revenues. The worst case scenario would mean revenues actually declining by £24m.

"Given the findings in the literature, the impact of an increase in the AR [additional rate] to 50p remains uncertain," the paper stated.

"However, if the behavioural response was around the midpoint of this range, it would suggest that the revenue raised by a 5p increase in the AR would be in the low single millions."

The country's three largest business groups have also warned the Scottish Government not to raise income tax.

Tim Allan from the Scottish Chambers of Commerce said in an after-dinner speech attended by the First Minister: "A high tax Scotland would be easy to achieve but the damage could take years to repair."

The amount of opinion polling on the subject has been limited.

One poll carried out by Survation for the campaign group 38 Degrees found widespread support for paying more income tax if the money was used to fund public services.

Of those polled, 60% said they would be willing to pay more while only 15% said they would not.

There is, of course, a difference between lending your support to a hypothetical tax increase to a pollster and how you feel when more of your money is taken from you at the end of the working month.