I had a stab at this "UK investment order" thing myself. In fact it was going to a larger project that I haven't really managed to get off the ground yet. Anyway, I came up with this:
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Do you have any money left over at the end of each month after meeting your everyday living costs?
Y Proceed to next step
N Reduce your living costs and/or increase your take-home income by all means necessary. Do not proceed any further until you have met this.
Do you have an Emergency Fund? Typical recommendation is 1 month's living expenses or £1000.
Y Proceed to next step
N Keep piling cash until your EF is adequate, then proceed to next step
Are you contributing enough towards your work pension to take advantage of the maximum employer match?
Y Proceed to next step
N Contribute the full amount required to gain your full employer match, then go back to step 1
Have you paid off your "bad debt" - Debt that is either at a higher interest rate AND/OR debt taken out to finance consumption
Y Proceed to next step
N Use all you spare cash to eliminate ALL bad debt, only proceed to next step when bad debt has been eliminated
Do you have a cash reserve? This expands the emergency fund to typically 3-6 months' living expenses and allows you to plan further ahead and gives you a buffer to put a plan in place if required rather than panicking at any setbacks
Y Proceed to the next step
N Build your cash buffer at least in parallel with the next steps in the process. Proceed to the next step when you feel comfortable doing so
You should have a positive net cashflow now, ie put yourself on a stable base ready to invest
Is your marginal tax rate in the higher-rate tax band (50-150k) after exploiting the full employer pension match?
Y Increase your personal pension contribution further until your taxable income falls into the standard rate and/or you have maxed the 40k annual pension allowance
N Skip the next 3 steps, down to LISA question
Do you still have spare cash to Invest?
Y Excellent, proceed to the next step
N Congrats, you've invested as much as you are able to currently in the most tax efficient manner
Are you still taxed at the higher marginal rate (40%+) after maxing out the annual allowance?
Y Consider taking advantage of Pension Carry Forward rules to continue to gain tax relief at the higher rate until you can get into the standard rate tax band
N Go to the next step
Are you still taxed at the higher rate after using as much Carry Forward as possible?
Y You'll have to take your pay some tax at 40% I'm afraid. Take it with grace and humility then go to the next step
N Great, you've dodged the higher rate band for this year. Move onto the next step.
Are you aged 18-40 and eligible for a Lifetime ISA (LISA)?
Y You should probably max out your LISA as a next step, as you will receive tax relief at any grow is shielded from any CGT, income, dividend or any other tax when you come to withdraw from it (current age >60). This beats both standard pension contributions (either direct employee contribution or salary sacrifice) and standard ISAs from a tax efficiency perspective.
N Too bad. Go to the next step.
Do you still have spare cash to Invest?
Y Excellent, proceed to the next step
N Congrats, you've invested as much as you are able to currently in the most tax efficient manner
Does your employer run salary sacrifice pension contribution scheme?
Y You should probably take advantage of this as the most efficient tax shield available to you. Put in as much as you can
N It's quite marginal between employee pension contributions and a standard ISA
Do you still have spare cash to Invest?
Y Fill up standard ISA allowance to annual £20k limit (less any LISA allowance you were elegible for)
N Congrats, you've invested as much as you are able to currently in the most tax efficient manner
Do you still have spare cash to Invest?
Y Invest in general taxable account
N Congrats, you've invested as much as you are able to currently in the most tax efficient manner
Do you still have spare cash to Invest?
Y Send it to me in cash in an unmarked brown evelope
N Congrats, you've invested as much as you are able to currently in the most tax efficient manner