A report released Tuesday by Florida Tax Watch shows the oil spill‘s impact has gone far beyond oil on the beaches, costing the state’s five westernmost counties hundreds of millions of dollars in business along with millions in tax revenue.

Those counties (Bay, Escambia, Okaloosa, Santa Rosa, and Walton) rely heavily on tourism, which is their largest source of jobs save for the military bases in the area. What’s more, unlike Florida’s other regions, their peak season comes during the summer months — when the oil was still gushing and fears of oil on the beaches were at their peak.

Between May and September of this year, sales were down more than 7 percent in the five counties, even as they increased slightly for the state as a whole, according to the report (.pdf).

Other tourism indicators were on an upswing in the period before the spill, and the region had been emerging from the recession faster than some other parts of Florida:

Prior to the spill, bed tax collections had increased in comparison with the previous year in every month except one during the thirteen month period of May 2009 to May 2010. However, collections decreased markedly in June (6 percent), July (21 percent), and August (22 percent) when compared with the same time period in 2009.

As the state and local governments in the hard-hit region prepare to file claims with BP to recoup their lost revenues,  one consideration is what those revenues would have been if the spill had never occurred. Based on the positive trends going into the crucial tourism season, the report estimates that the fallout from the spill:

o Reduced gross sales in NW Florida by $454 million

o Reduced taxable sales in NW Florida by $239 million

o Reduced state sales tax collections in NW Florida by $14.3 million

o Reduced local sales tax collections by $1.1 million

These are likely conservative estimates for several reasons: NW Florida’s taxable sales were consistently outperforming the rest of the state prior to the oil spill; there were increased promotional efforts in the region; tourism statewide has increased; and the spill cleanup injected extra money into the region’s economy.

Locals filing claims with the Gulf Coast Claims facility have also shown the pattern of improving sales that halted shortly after the Deepwater Horizon oil rig exploded. Some had wages and hours cut during the recession, and we’re expecting to have them restored. Others were expecting raises before companies were forced to cut back.

Also Tuesday, the Florida Retail Federation announced it was lobbying BP to foot the bill (an estimated $25 million) for a series of seven sales tax holidays, one weekend per month starting in February. A press release from the group notes that tax holidays have an inordinate power to draw shoppers, which could make for a cost-effective way to fuel recovery for businesses hurt by the spill.

“BP has not agreed to this proposal yet,” the group’s CEO Rick McAllister said in the release. “But we believe that this is a win-win-win situation for retailers in those five counties, BP and Florida’s economy.”