Since 2004, Royal Mail has increased postal rates (or tariffs) annually during the first week of April. It will be no different in 2008. Royal Mail has just announced new rates effective April 7, 2008.
Accompanying the new rates will be a batch of new Machins, issued a week or two before the rates take effect. Even though non-denominated (non-value indicated or NVI) Machins are used for first- and second-class rates for letters and large letters, there will still be a need for new denominated Machins. Generally about four to six new Machins are required.
For those that collect them, there will also be a set of new pictorial regionals, two each for Scotland, Wales, Northern Ireland and England.
The rate increases are uneven. First-class letters go from 34p to 36p, an increase of 6% (rounded to the nearest percent), but second-class letters jump 13% from 24p to 27p. The situation is reversed for large letters. The first-class rate increases 8% from 48p to 52p, but the second-class increase is only 5%, from 40p to 42p.
The rate for 20 gram letters to Europe increases 4% from 48p to 50p, and the rate for 10 gram letters to the rest of the world also increases 4% from 54p to 56p.
With this rate change, Royal Mail has gotten rid of the two zones for overseas mail going to destinations outside Europe. Zone 1 includes the Americas, the Middle East, Africa, the Indian sub-continent and most of Southeast Asia including Hong Kong. Zone 2 covers the rest of the world. The rate for zone 2 is currently higher than for zone 1 for any item weighing over 20 grams. Starting in April, there will be only one "rest of world" rate that will actually represent a small decrease for destinations that were part of zone 2.
You can find the new rates on Royal Mail's web site. For now, click on "Tariff 2008 prices" on the main page, but that reference may change.
I think it is very considerate for Royal Mail to publish the new rates more than three months in advance of the effective date. It certainly helps customers predict their postage costs. Compare that to the United States Postal Service, which didn't post its latest rates on its web site until the effective date of May 14, 2007. (The rates may have been available earlier through other communication methods, but the web site was full of Star Wars promotions rather than useful postal rate charts.)