Built a UK gilt yield calculator because premium bonds are fun but the expected return is worse
The basic attraction of gilts is that they are boring in exactly the right way. You can see the coupon, see the maturity, see the price, and work out a yield to maturity instead of vaguely hoping for luck.
That is the main contrast with premium bonds. Premium bonds have the tax-free wrapper and the tiny chance of a jackpot, but for most people the expected return is lower and the whole thing is fuzzier. If what you actually want is a place for cash with a known maturity and a better expected yield, gilts are often more interesting.
The point of the page is to make that comparison practical. Rather than manually clicking around bond pages and trying to estimate what tax does to the coupon stream, the tool lays out the whole gilt table, calculates raw yield to maturity, then recalculates it after taxing only the coupon payments while leaving the redemption gain alone.
That last part matters because the tax treatment is what makes some lower-coupon gilts look much more attractive for higher-rate taxpayers than the headline coupon alone would suggest. You do not pay income tax on the capital uplift from buying below par and being redeemed at par, so the split between coupon and capital return matters.
The way I would use the tool is simple: put in the tax rate, trim the maturity range to the part of the curve I actually care about, sort by post-tax yield, and then click through the names that still look sensible after filtering out strips and very long maturities.
The chart is there for a quick shape-of-the-curve view, but the table is the main event. That is where you can actually see whether the extra maturity risk is buying enough yield, and whether a short gilt is already good enough for the job.
I do not think this replaces proper thinking about inflation, reinvestment risk, or what role gilts are supposed to play in a portfolio. It is just a better first pass than comparing premium bonds to cash by feel.